US1920820A - Refining of brass - Google Patents

Description

Aug. 1, 1933.

c. A. ROSE El AL 1,920,820

REFINING OF BRASS Filed May 24. 1930 SCRAP BRASS ICAST INTOIANODES ELECTROLYZE SULPHATE SOLUTION OF CU,ZN

Cu Pb, SM CATHODE SUMES .CONTINUALLY WITH- DQAW ELECTROLYTE nacoven I METAL VALUES I EVAPORATE] I COOL Q I MOTHEQ'L'QUOR z-so CRYSTALS E' DISSOLVE Cu 0 H 50 ATTORNEY Patented Aug. 1, 1933 UNITED STATES PATENT OFFICE REFINING F BRASS Application May 24, 1930. Serial No. 455,168-

2 Claims.

This invention relates to the process of treating scrap brass for recovering copper and zinc therefrom, and more particularly to an electrolytic process in which the copper is recovered as cathode 5 copper and the zinc is recoveredin the form of zinc sulphate crystals.

The invention provides a process of the above nature which is substantially continuous and is carried out without the formation of undesirable by-products. The electrolyte is largely recovered and recirculated through the cells, so that the copper andzinc content of the active electrolyte is maintained substantially constant and the spent electrolyte, after the recovery of copper and zinc therefrom, is again utilized in the cyclic operation. The zinc is recovered in the form of crystals which may be purified or may be marketed as the final product.

The invention further consists in the new and novel features of operation and the new and orig- I inal arrangements and combinations of steps in the process hereinafter described and more particularly set forth in the claims. r

In the accompanying drawing the figure is a fiow sheet illustrating the steps of the present process.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims app'ended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner ofits organization may be better understood by referring to the following description in which a particular commercial embodiment thereof is disclosed. It will be understood, however, that the processes and the steps thereof may be modified in various respects without departing from the broadfspirit and scope of the invention.-

In the following description and inthe claims the various steps in the process and the details comprising the invention will be identified by specific names for convenience, but they are intended to be as genericin their application as the art will permit.

In accordance with the present invention the brass is cast into anodes which are electrolyzed in asulphate solution containing a predetermined amount of copper and zinc; The copper is deposited on the cathodes and is removed aselectrolytic copper. The copper and zinc content of the electrolyte is maintained within the desired range by constantly withdrawing a portion thereof in which the copper is depleted and the zinc con- 55 tent increased and adding additional quantities Y cathodes.

free sulphuric acid per of electrolyte having the original zinc and copper content.- This additional electrolyte is derived from a subsequent step in the process.

-The electrolyte which is withdrawn is concentrated and cooled to crystallize the zinc as zinc sulphate crystals which are removed and sold to the trade or treated byany desired purification process. The mother liquor, after the removal of the crystals, is diluted to its original volume and copper is added to increase the cop per content to that of the original electrolyte, after which it is introduced into the cells in the step above mentioned.

As a specific manner of carrying on the above process, the scrap brass is cast into anodes which are electrolyzed in cells through which an elec-- trolyte containing given percentages of copper and zinc and free sulphuric acid is continually circulated. v During this electrolysis the copper content of the electrolyte is continually depleted and the zinc content increased owing to the fact that both copper and zinc are dissolved from the anodes, whereas copper only is deposited at the The weight of copper deposited is so approximately equivalent to the amount of cop-- per and zinc which is dissolved from the anodes.

The electrolytic cells may be arranged so that the electrolyte flows through all of the cells in parallel, in which case the composition of the electrolyte will be the same in all cells. The cells may, however, be arranged in parallel groups, the cells of each group being arranged in cascade. In this case the incoming solution of high copper and low zinc content is applied to the upper cell of each series and flows through the cells of the series until it overflows from the lowest. During this passage through the cells the copper content is depleted and the zinc content increased to the point desired for the next step. '95

As a specific example, the solution which is fed into the upper cell may contain 75 grams copper per liter, 40 grams zinc per liter and grams free sulphuric acid per liter. The solution overflowing from the lowest cell may contain 100 15 grams copper, 100 grams zinc and 100 grams liter. The copper content of the solution withdrawn from the cells will be governed largely by the minimum con-.

tent with which'a firm coherent cathode deposit of copper can be obtained.

The electrolyte withdrawn from the cells is treated for the recovery-of the zinc content by being evaporated to sucha volume that when cooled it will be "super-saturated with zinc sulphate, but not super-saturated with copper sulphate.

The solution is then cooled to any convenient temperature, such as 20 C. and a portion of the zinc sulphate is allowed to crystallize out as zinc sulphate crystals. The amount of zinc sulphate which will crystallize out will depend upon the composition of the solution before evaporation and the relative volumes before and after evaporation. The evaporation should be carried to such a point that the weight of zinc contained in the crystals is approximately equal to the weight of zinc dissolved from the brass anodes in the electrolytic cells.

The zinc sulphate crystals may contain slight amounts of copper sulphate and other impurities and may be purified in any suitable manner. If desired, they may be marketed as crude zinc sulphate crystals. The crystals may be dissolved in water and the resultant solution purified by well known methods and either electrolyzed with insoluble anodes for the recovery of electrolytic zinc or evaporated for the recovery of pure zinc sulphate.

The mother liquor, after separation of the crude zinc sulphate crystals, is diluted with water to its .original volume. It should then contain approximately the same amount of copper as the electrolyte drawn from the cells and about the same amount of zinc as the solution originally applied to the cells.

The copper content of the solution is thenincreased to that of the original solution, for example, 75 grams per liter, by dissolving copper sulphate or copper oxide therein, or by circulating it through finely divided metallic copper in the presence of air. If copper oxide or metallic copper is used an equivalent amount of sulphuric acid must also be added to maintain the acid content of the solution constant.

The solution then contains approximately 75 grams copper, 40 grams zinc and 100 grams of sulphuric acid per liter and is recirculated by being applied to the electrolytic cells thereby completing the cycle. a

Any impurities, such as lead and tin, in the scrap brass may be recovered as anode slimes from the electrolytic cells and may be treated in any well known process for the recovery of the metal values therefrom.

Although certain novel features of the invention have been described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes in the'se'veral steps of the process and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The process of treating brass which comprises forming said brass into anodes, treating said anodes in cells containing an electrolyte of substantially 75 grams per liter copper and substantially 40 grams per liter zinc in sulphate solution, continuing said treatment until the zinc content is increased to approximately 100 grams per liter and the copper is decreased to approximately 15 grams per liter, continuously withdrawing portions of the electrolyte of the above concentration and continuously adding further corresponding quantities of electrolyte of the first mentioned composition, evaporating the portion so withdrawn to cause the same to be supersaturated with zinc sulphate, cooling to approximately 20 C.,whereby a portion of the zinc sulphate crystallizes, removing the mother liquor, diluting with water to its original volume and adding copper to bring the copper content to approximately 75 grams per liter and utilizing the same as the source of electrolyte for said cells.

2. An electrolytic process for treating brass which comprises forming said brass into anodes, electrolyzing said anodes in an electrolyte containing predetermined amounts of copper and zinc in sulphate. solution for the ,deposition of copper as cathode copper thereby decreasing the copper content and increasing the zinc content of said electrolyte, withdrawing portions of said electrolyte, replacing the electrolyte so withdrawn with substantially equivalent quantities of electrolyte having the composition of the initial electrolyte, forming a supersaturated zinc sulphate solution by evaporating the portions of electrolyte withdrawn, cooling said supersaturated solution thereby crystallizing out zinc sulphate, diluting the mother liquor to substantially the original value, increasing the copper content of said mother liquor to approximately that of the original electrolyte and recirculating same to the electrolytic cells.

CHARLES A.. ROSE. BERRY MARVEL OHARRA.

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